For example, in a so-called mega solar power station (large-scaled photovoltaic power station), a large number of photovoltaic panels are arranged. In the station, outputs from a predetermined number of photovoltaic panels are aggregated at a connection box. Then, the aggregated outputs are sent to a power conditioner (power conversion device) (see PATENT LITERATURE 1 (FIG. 1), for example).
On the other hand, in order to monitor whether a failure has occurred in any of photovoltaic panels, there have been proposed various technologies that transmit information of current/voltage outputted by the photovoltaic panels, by use of direct current power lines (see PATENT LITERATURE 1 to 3, for example). A typical transmission technology is power line communication (PLC). In a case where power line communication is used, voltage/current measuring devices and slave devices for power line communication are provided in each connection box, and each slave device transmits measurement information by use of a direct current electrical path, and a master device provided on the power conditioner side collects the measurement information.